The present invention is directed to a magnetic coupling for a device located inside a vacuum bulb of a tube which is mounted by shafts for rotation along an axis and has an outer ferromagnetic part and an inner ferromagnetic part mounted for rotation in the vacuum bulb. Such a magnetic coupling can serve the purpose of locking a cathode arrangement of a rotating X-ray tube.
A magnetic coupling is described by Von Kurt Dietz "Altes und Neues uber Rontgen-Rohren", Rontgenpraxis, S. Hirzel Verlag Stuttgart, 1964, pp. 31-32. A cathode arrangement in the interior of the vacuum housing is attached to a shaft extension of a rotatably mounted X-ray tube, which is referred to as a rotating X-ray tube. This cathode arrangement is likewise rotatably mounted within the tube. The cathode arrangement can be magnetically restrained by a device which is attached to the cathode arrangement. This device is composed of an inner part secured to the cathode device and of an outer part that embraces the rotating tube in the region of the inner part. The magnets are usually employed for these purposes.
What has proven disadvantageous is that during the heating and baking of the vacuum tube, the vacuum tube must be brought to a temperature which lies above the Curie point of a permanent magnet or that can at least have a partially demagnetizing effect thereon. Since the introduction of the magnetic field into the proximity of the cathode can produce undesirable deflection of the electron beam emanating from the cathode, this type of arrangement also causes problems.